AC temp differential

[Keith]

I seem to recall that a well functioning air conditioning unit cooled the ambient air by 20 degrees, is that right? It's a hot day here, and I'm getting ambient air inside the boat at the return at about 83 and it's coming out at 70. Sounds like it's not cooling like it should.

*

 

[HeyJude]

Our '05 Sea Ray 340DA started off with a delta of 18-20 that fell to 12-14 by 2010. The cooling water discharge was noticeably less & upon recommendation of SR forum guru I flushed the AC system with phosphoric acid to dissolve the minerals that had deposited themselves within the AC coils. Post procedure the cooling water flow increased by 30%, the outflow temp rose 10º & the delta returned to 18-20. The acid is a paint prep, available at HD & fairly benign to work with.

 

[FF]

Most air cond output readings are at the evap , about 40F is the goal.Below that and icing is a possibility .

Measuring at the end of a duct allows too many variables.

THe key to efficient air cond is in having a very efficient ducted return system.

 

[spcoolin]

FF wrote:
Most air cond output readings are at the evap , about 40F is the goal.Below that and icing is a possibility .

Measuring at the end of a duct allows too many variables.

THe key to efficient air cond is in having a very efficient ducted return system.

*Not really true...34 to 42 degrees is the target with a 15 to 18 degree TD...
<ul>[*]Higher than 18 degree TD usually means restricted air flow and is where you will see coil icing in ambient air temps below 68 degrees or higher depending on how restricted...[*]Less than 15 degree TD usually means a system problem...[/list]
These figures are what Cruisair & Marine Air design for...

Yes a long duct run can reduce TD a bit...

I do agree about the duct system needs to be efficient, but many times ducted return is anything but in a boat, and more often too small for the Btu design due to space restraints aboard....

Steve~

Marine-AC.com